1. Field of the Invention
This invention relates generally to supplying hydraulic fluid, such as lubricant, to a component and, in particular, to a fluid flow path in a rotating hub of clutch for a motor vehicle transmission.
2. Description of the Prior Art
The hub of a friction clutch or an overrunning clutch in an automatic transmission assembly transfers torque between an element of the clutch element and a shaft or another component that transmits torque in the assembly. In addition, such hubs carry hydraulic fluid, such as automatic transmission fluid (ATF), to lubricate and cool surfaces of the clutch, especially those surfaces that are subject to friction, fretting or chafing during in-service use. To provide fluid passageways, the hub is usually formed with a series of angularly spaced holes drilled radially through the hub thickness, through which holes fluid passes to the critical surfaces of the component. ATF fluid is continually deposited by being thrown radially outward against the inner surface of the component as the assembly operates.
Typically, hubs that are machined from a solid metal blank or forging, or by another forming method other than sheet metal forming, require machining an oil dam on the inner diameter of the hub to direct oil through radial drilled holes in order to cool the clutch and to prevent oil flow from the ends of the hub. Oil dams are, however, expensive to machine in such hubs.
Axially directed slots located at each radial hole are ineffective toward directing a sufficient volume of oil from the inside diameter of the hub to the radial holes because oil delivered to the hub inner diameter along the circumferential length of the hub between the slots will run off the end of the hub instead of flowing into the axial slots and radial holes.
There is a need in the industry, therefore, for a low cost technique that efficiently and effectively gathers and transports oil from the inner circumference of a hub to and through holes that pass through the wall thickness of a hub to facilitate lubrication and cooling of the critical surface of the component.